Environmental monitoring along the coast

Fish species that spend large portions of their lives in the coastal zone, such as perch, roach, eelpout, and wrasse, are influenced by many factors: fishing, climate, eutrophication, environmental toxins, food availability, and predation. The species present, their numbers, and their health provide clear signals about the state of the marine environment.

Thanks to decades of data from many areas, we can track long-term changes. For example, the results show that since the 1970s, catches of freshwater species in the Baltic Sea have increased, while saltwater species have decreased.

How our results are used

The data we collect is a vital piece of the puzzle in the work towards healthier seas and sustainable fish stocks. This information is used to assess the ecological status of coastal waters, monitor environmental quality objectives, and evaluate the effects of fisheries management measures. Results are also published in the annual fish and shellfish stock assessments in Swedish waters, which SLU Aqua publishes on fiskbarometern.se, providing a key knowledge base for fisheries management.

The results form the basis for both national and regional management and are also included in reporting to international collaborations and agreements, such as ICES, HELCOM, and OSPAR. The monitoring also contributes to research on how climate change, environmental impacts, and human activities like fishing affect our coastal areas.

National and regional environmental monitoring

Many fish surveys are conducted as part of national and regional environmental monitoring. Others take place in areas such as protected zones or regions with increased risks of environmental impact. We also conduct fish surveys to monitor species of particular interest, such as threatened or invasive species.

National integrated coastal fish monitoring

Integrated coastal fish monitoring has been carried out in seven areas – from Fjällbacka on the western coast to the Holmö Islands in the Norra Kvarken in the north of the Baltic Sea. The aim is to detect broad environmental changes by monitoring fish populations, fish health, and concentrations of environmental toxins in the fish.

The surveys include standardised fish surveys with coastal gillnets and fyke nets, as well as analyses of growth, reproduction, and health status of species like perch and eelpout. The results allow us to track environmental impacts – from individual fish to changes in entire fish communities.

The programme is conducted by SLU (fish stocks), the University of Gothenburg (fish health), and the Swedish Museum of Natural History (environmental toxins), and is funded by the Swedish Agency for Marine and Water Management. Raw data is stored in the KUL database. Results are published, among other formats, as fact sheets in SLU Aqua’s report series.

On the Swedish Agency for Marine and Water Management's website, you can read more about the Integrated coastal fish monitoring programme, which is part of the national environmental monitoring programme area for Coast and Sea.

Regional kustfiskövervakning

The regional monitoring is conducted in about twenty areas in collaboration with the county administrative boards. The aim is to follow the development of fish stocks in different coastal environments – from archipelagos to fjords and open coastal stretches.

The areas are chosen to reflect both regional variations and long-term trends. Some are located in relatively unaffected environments, others in areas with impacts from buildings, industry or fishing.

The surveys are carried out annually using standardised methods (nets and gillnets) and include species such as perch, pike, flounder, cod, eel and wrasse.

The monitoring is financed by the Swedish Agency for Marine and Water Resources in collaboration with the respective county administrative boards. Raw data is stored in the KUL database. Results are published as fact sheets in SLU Aqua's report series.

For more information on the regional environmental monitoring in the "A balanced marine environ­ment, flourishing coastal areas and archipelagos" programme, you can visit the websites of the county administrative boards.

Coastal trawling and egg surveys on the west coast

To track the development of the coastal and benthic fish community on the West Coast, SLU Aqua conducts annual coastal trawl surveys, from the offshore bank of Fladen in the Kattegat to Singlefjorden near the Norwegian border. 

The survey takes place in September at around 35 fixed stations, from fjords to offshore areas. It provides valuable information on species composition, recruitment, and the presence of benthic fish – with a particular focus on cod.

The trawl survey is funded by the Swedish Agency for Marine and Water Management. Raw data is stored in the Fishdata2 database.

Along parts of the West Coast, SLU Aqua also performs egg surveys in the water column to track spawning activity in cod and other winter-spawning fish species in archipelago and fjord environments.

Monitoring of vendace in the Gulf of Bothnia

Surveys of vendace, which inhabit the water column (pelagic zone), are conducted using acoustics (echo sounding). The echo sounders register the quantity of fish along a pre-determined route. Periodic trawling is also carried out to estimate size composition. Additionally, vendace is sampled through onboard and harbour sampling within the commercial fishery.

The raw data collected is stored in the KUL database.

Coastal fish surveys in practice

Fish surveys are usually conducted in August, when the weather is stable and most coastal fish have finished spawning. Some species that prefer colder water temperatures are monitored later in the autumn. Targeted surveys, such as those focusing on spawning fish, are carried out at other times of the year.

To track changes over time and compare different areas, we always use standardised methods when conducting fish surveys. This means the same type of equipment is used in the same way, at the same time of year, year after year. All species are recorded – not just those of interest to fishing. We also record species, numbers, size, and any external signs of disease. We collect fish for age analysis and health assessments.